Electrodes are used in the medical field for applications such as stimulation, sensing, ablation and defibrillation.
Typically, such a lead is in the form of a catheter which is inserted through a blood vessel of a patient's body to the desired location in the patient's body.
The thinner the electrical lead, the easier it is to insert and manipulate. Further, by making the lead thinner, the patient suffers less discomfort.